Hydrazones of pyrazolopyridine carboxylic acids and esters

ABSTRACT

1. A COMPOUND OF THE FORMULA   1-R2,3-R3,4-(Y-C(-X)=N-NH-),5-(R1-OOC-),6-R6-1H-PYRAZOLO-   (3,4-B)PYRIDINE   WHEREIN R1 IS HYDROGEN, LOWER ALKYL OR PHENYL-LOWER ALKYL, R2 IS HYDROGEN, LOWER ALKYL OR BENZYL, R3 IS HYDROGEN OR LOWER ALKYL, R6 IS HYDROGEN OR LOWER ALKYL, X IS HYDROGEN, PHENYL OR R7, R8-PHENYL-LOWER ALKYL AND Y IS R7, R8PHENYL OR R7, R8-PHENYL-LOWER ALKYL, R7 AND R8 EACH IS HYDROGEN, HALOGEN, LOWER ALKYL OR LOWER ALKOXY, AND PHYSIOLOGICALLY ACCEPTABLE ACID ADDITION SALTS THEREOF.

United States Patent U.S. Cl. 260-440 G Claims ABSTRACT OF THE DISCLOSURE New hydrazones of pyrazolopyridine carboxylic acids and esters having the general formula and salts thereof which are antimicrobial agents and central depressants are the subject of this invention.

This application is a division of application Ser. No. 208,449, filed Dec. 15, 1971, now US. Pat. 3,773,777, granted Nov. 20, 1973, which is in turn a continuationin-part of application Ser. No. 42,415, filed June 1, 1970, now abandoned, which is in turn a continuation-in-part of application Ser. No. 833,672, filed June 16, 1969, now abandoned.

BRIEF SUMMARY OF THE INVENTION This invention relates to new hydrazines, hydrazides and hydrazones of pyrazolopyridine carboxylic acids and esters, and salts thereof. The new hydrazines, hydrazides and hydrazones have the structural formulas R R4 R X NN I I--N=li3Y I s,

R,--- -O00R R 000R l J and i N N N N In formulas I and H, R represents hydrogen or lower alkyl, R represents hydrogen, straight or branched alkyl up to 12 carbons, preferably lower alkyl or phenyl-lower alkyl, R represents hydrogen, lower alkyl, phenyl, phenyllower alkyl, substituted phenyl-lower alkyl of cycloalkyllower alkyl, R represents hydrogen, lower alkyl, phenyl or substituted phenyl, R represents hydrogen, lower alkyl, trihalo (hydroxy) lower alkyl, trihalo-lower alkyl or phenyl, R represents hydrogen or lower alkyl, R represents hydrogen, lower alkyl, phenyl or phenyl-lower alkyl, X represents hydrogen, hydroxy, lower alkyl, hydroxylower alkyl, phenyl, substituted phenyl, phenyl-lower alkyl or substituted phenyl-lower alkyl, Y represents lower alkyl, phenyl, hydroxy-lower alkyl, substituted phenyl, phenyl-lower alkyl or substituted phenyl-lower alkyl and together X and Y are cycloalkyl or S-nitro-Z-furyl.

The lower alkyl groups represented by the symbols are straight or branched chain hydrocarbon groups of up to seven carbon atoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl and the like.

Similar lower alkyl groups are part of the phenyl-lower alkyl and cycloaIkyl-lower alkyl substituents. The substituted phenyl and phenyl-lower alkyl groups include phenyl rings bearing one or two substituents, e.g., R R3 phenyl wherein R and R each is halogen, especially chlorine or bromine, lower alkyl or lower alkoxy. Thus there are included phenyl, chlorophenyl, e.g., o-, mor pchlorophenyl, bromophenyl, o-, mor p-tolyl, 2,5-dichlorophenyl, 3,5-dimethylphenyl, 3,4-dimethoxyphenyl, benzyl, phenethyl, 0-, mor p-chlorobenzyl, 3,5-dichlorobenzyl, p-methoxyphenyl and the like.

The cycloalkyl groups are cycloaliphatics having three to seven carbons, e.g., cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl.

Preferred compounds of formula I are those in which R is hydrogen, R is hydrogen, alkyl of up to 12 carbon atoms (particularly lower alkyl of up to 8 carbon atoms), or phenyl-lower alkyl, R is hydrogen, lower alkyl or phenyl-lower alkyl, R is hydrogen or lower alkyl, R, is hydrogen, lower alkyl or phenyl, R is hydrogen or lower alkyl and R is hydrogen or lower alkyl. Preferred compounds of formula II are those in which R R R and R have the meanings just referred to, X is hydrogen, lower alkyl, hydroXy-lower alkyl, phenyl or phenyl-lower alkyl, Y is lower alkyl, phenyl or phenyl-lower alkyl and tov gether X and Y are cycle-lower alkyl (particularly cyclohexyl) Preferably when either R or R is other than hydrogen or lower alkyl, the other is hydrogen. The trihalo- (hydroxy)lower alkyl group is preferably (l-hydroxy- 2,2,2-trichloro)ethyl. The preferred halogens are chlorine and bromine, especially the first.

Especially preferred compounds of formula I are those in which R is hydrogen, R is hydrogen or lower alkyl, especially ethyl, R is hydrogen, ethyl or benzyl, R R and R each is hydrogen or methyl. Especially preferred compounds of formula II are those in which R R and R are the same as specified for formula I and X and Y each is lower alkyl, especially methyl or together are cyclohexyl. R is hydrogen or methyl in each instance.

DETAILED DESCRIPTION The new compounds are formed by the following series of reactions. The symbols in the structural formulas have the same meanings previously described.

A S-aminopyrazole of the formula (III) Its--- -\NJNH2 I I 1 12 is produced as described in British Pat. 1,057,740, published February 8, 1967, by ring closure of an aldehyde or ketone hydrazone of the formula (IV) R9 wherein R is the same as previously defined and R and R each is hydrogen, lower alkyl, phenyl or phenyl-lower alkyl. The cyclization is effected by heating at a temperature of about to C. in an inert liquid solvent, e.g., an alcohol like methanol, ethanol, butanol or the like, preferably in the presence, of a catalyst, e.g., alcoholates like alkali metal alcoholates particularly butylates such as 7 sodium butylate.

This S-aminopyrazole is reacted with an alkoxymethylene malonic acid ester of the formula V alkyl-O COORr wherein R represents lower alkyl, e.g., ethoxy methylene malonic acid diethyl ester or the like. This may be effected by heating the reactants at a temperature of the order of 120 C. for several hours, and results in a compound of the formula (VI) R3 R I ll 4120 l E R2 The alkoxymethylene malonic acid esters of formula V are known compounds and are produced like ethoxymethylene malonic acid diethyl ester [Organic Synthesis 28, 60-2 (1948)].

Cyclization of a compound of formula VI produces a product of the formula wherein R is hydrogen and R R R and R correspond respectively to R R R and R of the starting material. This reaction is carried out by heating the S-pyrazolylaminomethylene malonic acid ester of formula VI in an inert organic solvent such as diphenyl ether at a temperature of about 230 to 260 for several hours while removing, e.g., by distillation, the alcohol -R OH. The product is then separated from the solvent, e.g., by fractional distillation.

Alternatively, instead of cyclizing the malonic acid ethyl ester compound of formula VI in an inert organic solvent at about 230 to 260 as described above, this product also undergoes cyclization by treatment with phosphorous oxychloride producing directly the intermediate of the formula COORi Derivatives of formula VII in which R is hydrogen and R is other than hydrogen may also be prepared by reacting a S-aminopyrazole of formula III with an acyl malonic acid ethyl ester of the formula (Va) 0 000R] Ru- CH COORi wherein R is an aromatic or heterocyclic nucleus like phenyl, naphthyl, furyl, pyridyl, pyrimidyl, pyrazinyl or the like.

This material is processed as described above through the reaction with the alkoxymethylene malonic acid ester of formula V and cyclization of the product of formula VI thus obtained to produce a compound of formula VII or VIIa. The CH -R group remains intact through these reactions.

At this point, the compound of formula VII or VIIa, having in the l-position the CH R substituent, is oxidized with an oxidizing agent like selenium dioxide in a high boiling solvent like diethyleneglycol dimethylether at about C. This yields a compound of formula VII or VIIa wherein R is hydrogen.

The free acid, i.e., R is hydrogen, may be obtained rorn the ester obtained as described above by hydrolysis, e.g., treatment with aqueous sodium hydroxide solution.

Products of formula VII wherein R is lower alkyl or phenyl-lower alkyl are produced from those wherein R is hydrogen by alkylation, e.g., treatment of the latter with an alkylating agent such as an alkyl halide or aralkyl halide like ethyl iodide or benzyl bromide, in an inert organic solvent such as dimethylformamide in the presence of an alkali metal carbonate such as potassium carbonate.

Reaction of any of the foregoing products of formula VII wherein R is lower alkyl or phenyl-lower alkyl with at least an equivalent amount of hydrazine, substituted hydrazine or a salt thereof, e.g., hydrazine hydrate, hydrazine hydrochloride, methylhydrazine, phenylhydrazine or the like yields a compound of formula I. The material of formula VII is dissolved in an inert, preferably dry, organic solvent, e.g., an alcohol like absolute ethanol and the hydrazine added, preferably alone with a small amount of a metal like zinc chloride. The mixture is heated, e.g., at reflux temperature, for several hours, then the product is isolated.

Alternatively, a compound of formula VII wherein R is hydrogen may first be converted to its chloro analog (i.e., the hydroxy group is replaced by chlorine) upon treatment with phosphorous oxychloride. The chloro compound of formula V'IIa, which may also be obtained by cyclization of a compound of formula VI by means of phosphorous oxychloride, is then treated with the hydrazine to obtain a product of formula I.

The hydrazine of formula I (wherein R and R are both hydrogen) is converted to the hydrazine of formula II by reaction with a carbonyl compound, e.g., an aldehyde or ketone, in an inert organic solvent such as an alcohol. Such carbonyl compounds include, for example, acetaldehyde, propionaldehyde, butyraldehyde, benzaldehyde, phenylacetaldehyde, phenylpropionaldehyde, pchlorobenzaldehyde, m bromobenzaldehyde, 2,5 dichlorobenzaldehyde, p methoxybenzaldehyde, acetone, dihydroxyacetone, chloral, chloral hydrate, methyl ethyl ketone, methyl propyl ketone, acetophenone, phenylpropyl ketone, p chlorophenyl ethyl ketone, cyclopro panone, cyclobutanone, cyclohexanone and the like.

A hydrazine of formula I wherein R is hydrogen and R is lower alkyl or cycloalkyl may alternatively be obtained by the catalytic reduction of an appropriately substituted compound of formula II.

The bases form salts by reaction with equivalent amounts of the common inorganic and organic acids. Such salts include the hydrohalides, e.g., hydrobromide, hydrochloride, sulfate, nitrate, phosphate, acetate, citrate, oxalate, tartrate, maleate, succinate, benzoate, ascorbate, alkanesulfonate, e.g., methanesulfonate, arylsulfonate,

e.g., benzenesulfona'te, etc. It is freguently convenient to purify or isolate the product by forming an insoluble salt. The base may be obtained by neutralization and another salt then formed by treatment with appropriate acid.

The compounds of this invention are useful as antimicrobial agents, e.g., in combatting infections due to organisms such as T richomonas vaginalis, Staphylococcus aureus or Trychophyton m entagrophytes. For example, they may be administred orally to various mammalian species, e.g., mice in an amount of about 5 to 25 mg./- kg./day, preferably in 2 to 4 divided doses, in any of the conventional oral dosage forms, or topically in creams in equivalent amounts. They may be used as surface disinfectants. About 0.01 to 1.0% by weight of any of these substances may be dispersed on an inert solid or in a liquid such as water and applied as a dust or spray or incorporated in a soap or other cleaning agent such as a solid or liquid detergent composition. The latter may be used, for example, in general cleaning, in cleaning dairy barns or dairy, food handling or food processing equipment.

The new compounds of this invention are central nervous system depressants and may be used as tranquilizers for the relief of anxiety and tension states, for example in mice, rats, dogs and other mammalian species, in the same manner as chlordiazepoxide. For this purpose these compounds may be incorporated in a conventional dosage form such as tablet, capsule, injectable or the like, along with the necessary carrier material, excipient, lubricant, buffer or the like, for oral or parenteral administration in single or divided doses of about 1 to 50 mg./kg./day, preferably about 2 to mg./kg., two to four times daily.

The new compounds also increase the intracellular concentration of adenosine 3',5 cyclic monophosphate, and thus by the administration of about 1 to 100 mg./- kg./day, preferably about 10 to 50 mg./kg. in single or two to four divided doses in conventional oral or parenteral dosage forms such as those described above may be used to alleviate the symptoms of asthma.

The following examples are illustrative of the invention. All temperatures are on the centigrade scale.

EXAMPLE 1 1-Ethyl-4-hydrazinolH-pyrazolo [3,4-pyridine-5- carboxylic acid, ethyl ester (a) {[(1 Ethyl 5 pyrazolyl)amin0]methylene} malonic acid diethyl ester 245 g. 1 ethyl 5 aminopyrazole (2.2 mole) and 476 g. ethoxymethylene malonic acid diethyl ester (2.2 mol.) are heated to 120 (bath temperature) for 2 hours with stirring. The ethanol formed by this reaction is removed by means of a water aspirator. Then vacuum distillation (b.p. 0.1 154160) yields 520 g. (84% of theory) of a quick crystallizing oil of {[(1 ethyl 5 pyrazolyl)amino]methylene} malonic acid diethyl ester, m.p. 50-5 3 The compound is recrystallized from N-hexane, rn.p. 55-57.

The hydrochloride salt is formed by treating the above product with dilute ethanolic hydrogen chloride solution.

(b) 1 Ethyl 4 hydroxy 1H pyrazolo[3,4-b]- pyridine 5 carboxylic acid and ethyl ester. 253 g. {[(1- ethyl 5 pyrazolyl)amino]methylene} malonic acid diethyl ester (0.09 mol.) are dissolved in 770 g. of diphenyl ether. The reaction mixture is heated to 235-250 (bath temperature) and allowed to react at this temperature for 1-2 hours while the resulting ethanol is continuously distilled off. The last amount of alcohol is removed by means of a water aspirator. The diphenyl ether is separated by distillation with a fractionating column in vacuo. The 1 ethyl 4 hydroxy 1H pyrazolo[3,4 -b]- pyridine 5 carboxylic acid ethyl ester is obtained at b.p. 0.05 115120, yield 195 g.:92% of theory, m.p. 8587. The compound is recrystallized from benzene (90 to 100), m.p. 87-89". Hydrolysis of this product with aqueous sodium hydroxide yields 1 ethyl 4 hy- 6 droxy 1H pyraz'olo[3,4 bJpyridine 5 carboxylic acid, m.p. 201-202.

(c) 4 Ethoxy 1 ethyl 1H pyrazolo[3,4 b]pyridine 5 carboxylic acid and ethyl ester. In a solution of 259 g. (1.1 mol.) 1 ethyl 4 hydroxy 1H pyrazolo[3,4 bJpyridine 5 carboxylic acid ethyl ester in 1700 ml. dimethylformamide, 400 g. of well pulverized potassium carbonate and 300 g. of ethyliodide are introduced. The reaction mixture is stirred for 7 hours at 65 and filtered under suction, while hot, from excess potassium carbonate. Upon standing overnight, 165 g. of lethyl 4 ethoxy 1H pyrazolo[3,4 blpyridine 5- carboxylic acid ethyl ester crystallize out of the solution, m.p. 112115. After evaporation of the mother liquor, an additional g. are obtained. The total yield amounts to of theory. The compound is recrystallized from benzene (l00), m.p. 113-115.

By hydrolizing this product as in part (b) 4-ethoxy-1- ethyl-lH-pyrazolo[3,4-bJpyridine-5-carboxylic acid is obtained, m.p. l98199.

d) l-Ethyl-4-hydrazino-lH-pyrazolo [3 ,4-b pyridine-5- carboxylic acid ethyl ester. 316 g. l-ethyl-4-ethoxy-1H- pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester (1.2 mol) are dissolved in 4800 ml. of absolute alcohol. Into this solution, 72 g. of hydrazine hydrate (100%) and 0.4 g. zinc chloride are added. After refluxing for 4 hours, the hot solution is filtered, evaporated to dryness in vacuo and the White crystalline residue is crystallized from a benzol benzene mixture 1:3. There are obtained 250 g. of l-ethyl- 4-hydrazino-lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester, m.p. 139-140.

The hydrochloride is formed by adding to a solution of 5 grams of the above obtained hydrazine in 100 ml. of absolute alcohol, with cooling, 5 ml. of an alcoholic solution of hydrogen chloride (6.3 N). A white crystalline precipitate forms immediately. The mixture is diluted with anhydrous ether, filtered and washed with anhydrous ether. The product is allowed to air-dry overnight.

The l-ethyl-4-hydrazinolH-pyrazolo 3,4-b] pyridine-5- carboxylic acid, ethyl ester, hydrochloride, is recrystallized from a mixture of acetonitrile and absolute alcohol, mp. 210-212.

EXAMPLE 2 1 Ethyl 4 (2 isopropylidenehydrazino)-1H-pyrazolo [3,4-b]pyridine-S-carboxylic acid, ethyl ester hydrochloride A solution of 8.4 grams of 1-ethyl-4-hydrazino-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester in 100 ml. of acetone is refluxed for one hour. To the cooled solution of the isopropylidene hydrazine, m.p. 9293 there is added, with cooling, 10 ml. of an alcoholic solution of hydrogen chloride (6.98 N). A white crystalline precipitate forms immediately. The mixture is diluted with ml. of anhydrous ether to aid in filtering, and the solid filtered, washed with anhydrous ether, and dried at 1 mm. and 110 overnight. The product l-ethyl-4-(2- isopropylidenehydrazino) 1H pyrazolo[3,4-b]pyridine- S-carboxylic acid ethyl ester, hydrochloride, melts at 193- 196", with preliminary softening at EXAMPLE 3 1-Ethyl-4 (2-isopropylidenehydrazino -lH-pyrazolo [3,4-b]pyridine-S-carboxylic acid, hydrochloride By treating the 1-ethyl-4-hydroxy-1H-pyrazolo[3,4-b]- pyridine-5-carboxylic acid ethyl ester in Example 1(b) with hydrazine and acetone as in Example 1(d) and 2, 1 ethyl 4 (2-isopropylidenehydrazino)-1H-pyrazolo- [3,4-b]pyridine-S-carboxylic acid, hydrochloride, is obtained.

EXAMPLE 4 4 (2 Benzylidenehydrazino) l ethyl-lH-pyrazolo [3,4-b] pyridine 5 carboxylic acid, ethyl ester hydrochloride By substituting an equivalent amount of benzaldehyde for the actone in the procedure of Example 2, 4-(benzylidenehydrazino) l ethyl-lH-pyrazolo[3,4-b]pyridinecarboxylic acid, ethyl ester hydrochloride is obtained, m.p. 136-137. Upon saponification, the free acid melts at 225-226.

EXAMPLE 5 4 (2 Cyclohexylidenehydrazino)-1-ethyl-1H-pyrazolo [3,4-b]pyridine-S-carboxylic acid, ethyl ester, hydrochloride By substituting cyclohexanone for acetone in the procedure of Example 2, 4-(2-cyclohexylidene hydrazino)- 1 ethyl lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid, ethyl ester, m.p. 127, and hydrochloride, m.p. 198-199 are obtained. Upon saponification, the free acid melts at 219.

EXAMPLE 6 1 Benzyl 4 (2-isopropylidenehydrazino)-1H-pyrazolo [3,4-b]pyridine-S-carboxylic acid, hydrochloride, and 1 benzyl 4 (2-benzylidenehydrazino)-1H-pyrazolo- [3,4-b]pyridine-5-carboxylic acid hydrochloride 8 ethyl ester, m.p. 159 161 is obtained. The hydrochloride melts at 215. Then by treating this hydrazine with acetophenone according to the procedure of Example 2, l-benzyl-4-(2-phenethylidenehydrazino)-1H-pyrazolo[3,4 b]- pyridine-S-carboxylic acid, ethyl ester, hydrochloride is obtained.

EXAMPLE 8 1-Benzyl-4-[ (S-nitrofurfurylidene) hydrazino] -1H-pyrazolo[3,4-b]pyridine-S-carboxylic acid, ethyl ester By treating 1-benzyl-4-ethoxy-lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester with hydrazine hydrate as in Example 1 and then treating the product with 5- nitrofurfurylaldehyde according to the procedure of Example 2, the above named compound, m.p. 205-207", is obtained.

EXAMPLE 9 1-Ethyl-4- [S-nitrofurfurylidene hydrazino]- lH-pyrazolo [3,4-b]pyridine-S-carboxylic acid, ethyl ester By treating the product of Example 1(d) with S-nitrofurfuraldehyde according to the procedure of Example 2, the above named product, m.p. 228229, is obtained.

By using the S-aminopyrazolo with the substituents indicated in the first column below in place of l-ethyl-S- aminopyrazole and following the procedure of Example 1, alkylating with ethyl iodide or benzyl bromide as in part (0), there are obtained the 1H-pyrazolo[3,4-b]pyridine-S-carboxylic acids and esters of formula VII with the substituents indicated in the second column (R is hydrogen):

S-aminopyrazolo Pyrazolopyridine Example R2 R3 R11 R1 R2 R3 10 O'ClCdHACIIZ CH3 H C2H o-ClCoH4CH CH;

11 CH3 H C 2H: CH

H OH: H CH2 12 Same as above II 0211 CzH5 Same as above. H 13 H H H C3117 H 14" D-CIOQH4CH2 II I]: 02115 p-C1CaH4CHz II 15 p-Clc HiCHa H H H p-ClCgILCHz H 16 CIHa OH; H CzH (IJHa CH CsHaCH CaHsCH 17 CH3 (CH3)zCH H C2H5 CH3 (CH3)2CH H (CH2)aCHa C2H5 0111 H CH H C2115 C2H5 CH3 H H C211 C2115 CH(CH3)2 H C5115 H O2H CaHy CoHa O H C5H5CH2 C2H 0211 H 23 C5115CH2 C5115 H C1115 C5H5CH2 CoHs and benzylidene hydrazine hydrochloride, respectively, are obtained, as the free carboxylic acid or ethyl ester, respectively.

EXAMPLE 7 1 Benzyl 4 (2-phenethylidenehydrazino)-lH-pyrazolo [3,4-b]pyridine-5-carboxylic acid, ethyl ester, hydrochloride Treatment of each of the foregoing compounds of formula VII with hydrazine hydrate as in Example 1(d) yields the corresponding hydrazine. Treatment of each of the hydrazines thus obtained with acetone as in Example 2 yields the 4-(isopropylidenehydrazino)-1H-pyrazolo[3,4-b]pyridine carboxylic acid, hydrochloride, or ester thereof, having the same substituents R R and R listed in the second column above. Similarly, by substituting for the acetone an equivalent amount of benzaldehyde, p-chlorobenzaldehyde, cyclopentanone or acetophenone, respectively, the 4-benzylidene hydrazine, 4-(4-chlorobenzylidene)hydrazine, 4-cyclopentylidene hydrazine and 4-( l-phenethylidene)hydrazine and hydrochloride salt, respectively, are obtained.

The following additional compounds are produced by the procedure of Example 1 9 10 NHNH, equivalent amount of alcoholic hydrogen chloride and A precipitating the hydrochloride thus formed with anhydrous ether. 000R EXAMPLE 35 X y 5 4-(2-Acetylhydrazino)-1-ethyl-lH-pyrazolo[3,4-b]pyrif N dine-S-carboxylic acid ethyl ester R2 To 25 ml. of acetic anhydride there is added 3 grams R R M.P. Example RI 2 a o of 4-(Z-hydrazino)-1-ethyl-1H-pyrazolo[3,4-b]pyrid1ne-5- 24 igs & f} 3853 0 (H01) 10 carboxylic acid, ethyl ester. The mixture is heated at 100 2 5 a)a H 136138 for one hour and is then cooled and filtered. The solid is recrystallized from 95% ethanol, mp. 221-222. The following additional compounds are produced by EXAMPLE 36 the procedure of Example 4-(2,2-Diacetylhydrazino)-l-ethyl-lH-pyrazolo[3,4-b]

X pyridine-S-carboxylic acid, ethyl ester NHN=(IJY To ml. of acetic anhydride there are added 3 grams R3 of 4-(2-hydrazino)-1-ethyl-1H pyrazolo[3,4 b]pyridine- Tl 20 S-carboxylic acid, ethyl ester. The mixture is heated at N 100 for about one hour and is then cooled and filtered to N N remove the monoacetylated derivative. The filtrate is stirred with 100 ml. of ice water to hydrolyze the unre- Example R1 R2 Ra X Y M.P.

H CH CH (CH CH 156.(HC1) :31:11: Ffihm. 85%: H be? 3 0H, 3 149 0101) 29 or 5 CH3 H CH3 CH3 211-21a (H01) 30 or 5 CH(CH3)2 H CH3 CH3 215-21s (H01) EXAMPLE 31 acted acetic anhydride. The solid which precipitates is 1-Ethy1-4- (2-phenylhydrazino) -lH-pyrazolo [3 ,4-b] pyridine-5-c arboxylic acid, ethyl ester By substituting an equivalent amount of phenylhydrazine for the hydrazine hydrate in the procedure of Example 1(d), 1-ethyl-4-(2-phenylhydrazino)-1H-pyrazolo- [3,4-b]pyridine-5-carboxylic acid, ethyl ester, mp. 176-- 177, is obtained.

EXAMPLE 32 1-Ethyl-4-(2-tert.butylhydrazino) -1H-pyrazolo [3 ,4-b] drazino]-1H-pyrazolo[3,4-b1pyridine 5 carboxylic acid ethyl ester By substituting an equivalent amount of dihydroxyacetone for the acetone in the procedure of Example 2, 1- ethyl-4-[[2-hydroxy 1 (hydroxymethyl)ethylidene]hydrazino]-1H-pyrazolo[3,4-b]pyridine 5 carboxylic acid, ethyl ester, m.p. 175-177 is obtained.

EXAMPLE 33 1-Ethyl-4-(t-tert.butylhydrazino )-1H-pyrazolo [3 ,4-b] pyridine-S-carboxylic acid, ethyl ester, hydrochloride By substituting an equivalent amount of tertiarybutylhydrazine for the hydrazine in Example 1(d) 1-ethyl-4- (2-tert, butylhydrazino)-lH-pyrazolo[3,4-b]pyridine 5- carboxylic acid, ethyl ester, hydrochloride is obtained.

EXAMPLE 34 1-Benzyl-4-(2,2-diethylhydrazino -1H-pyrazolo [3,4-b] pyridine-S-carboxylic acid, ethyl ester, hydrochloride filtered and washed with water. The 4-(2,2-diacetylhy drazino)-l-ethyl-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid, ethyl ester is crystallized from hexane, m.p. ll3-ll4.

EXAMPLE 37 1-Ethyl-4-hydrazino-lH-pyrazolo [3 ,4-b] pyriidne-S- carboxylic acid ethyl ester (a) 4-Chloro-1-ethyllH-pyrazolo [3,4-b]pyridine-5-carboxylic acid ethyl ester. A mixture of 23.5 g. of 1-ethyl-4- hydroxy-lH pyrazolo [3,4 b]pyridine-5 carboxylic acid ethyl ester (0.1 mol.) and 150 ml. of phosphorous oxychloride is refluxed for four hours. Subsequently the excess phosphorous oxychloride is removed by distillation in vacuo. As soon as the phosphorous oxychloride has been removed, the oily residue solidifies on cooling. It is treated with water and filtered under suction to obtain 4-chloro-1- ethyl-lH-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (24.5 g.) m.p. 55-60 C. The product is recrystallized from n-hexane (22.5 g.=87%), m.p. 62.

b) 1-Ethyl-4-hydrazinolH-pyrazolo 3,4-b] pyridine-5- carboxylic acid ethyl ester. To a solution of 5.08 g. of 4- chloro-l-ethyl-lH-pyrazolo[3,4-b] pyridine 5 carboxylic acid ethyl ester (0.02 mol.) in 50 m1. of benzene are added 2.5 g. of hydrazine hydrate (0.05 mol.). This mixture is stirred at room temperature for 4 days. After this time, the separated hydrazine hydrochloride is filtered under suction and the filtrate is evaporated in vacuo to dryness. The residual product, 1-ethyl-4-hydrazino-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester, is recrystallized from benzene, m.p. 139140.

EXAMPLE 38 l-Ethyl-4-phenylhydrazino-1H-pyrazolo [3 ,4-b pyridine- S-carboxylic acid ethyl ester A solution of 25.3 g. of 4-chloro-1-ethyl-lH-pyrazolo [3,4-b]pyridine-S-carboxylic acid ethyl ester (0.1 mol.) and 21.6 g. of phenylhydrazine (0.2 mol.) in 200 ml. of benzene is refluxed for four hours. After cooling, the separated phenylhydrazine hydrochloride is filtered under suction and the filtrate is evaporated in vacuo to dryness. The product, l-ethyl-4-phenylhydrazino-lH-pyrazolo[3,4-

b]pyridine--carboxylic acid ethyl ester is recrystallized from 96% ethanol, m.p. 176-177.

EXAMPLE 39 4- (Z-Cyclohexylidenehydrazino)-1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester (a) [[[1-(2-furyl)methyl-5 pyrazolyl] amino1methylene]malonic acid diethyl ester. 163 g. of 1-(2-furyl) methyl-S-aminopyrazole (1 mol.) and 216 g. of ethoxymethylene malonic acid diethyl ester (1 mol.) are heated to 130 (bath temperature) until the theoretical amount of alcohol is distilled off. The remaining oil, [[[1-(2-furryl)methyl 5 pyrazolyl]amino]methylene]malonic acid diethyl ester, is recrystallized from methanol, yield 280 g. (84%) m.p. 84-86.

(b) 4-hydroxy-l-(2-furyl)methyl-lH-pyrazolo[3,4 b] pyridine-S-carboxylic acid ethyl ester. 250 g. of [[[1-(2- furyl)methyl-S-pyrazolyl]amino]methylene]malonic acid diethyl ester (0.75 mol.) are dissolved in 1 liter of diphenyl ether and heated to 240 for two hours. The ethanol formed is continuously distilled ofi. The solvent is removed in vacuo. The 4-hydroxy-l-(2-furyl)methyl-1H-pyrazolo[3,4-b]-pyridine-5-carboxy1ic acid ethyl ester remains and is recrystallized from methanol, yield 248 g. (86% m.p. 103106.

(c) 4-ethoxy-1-(2-furyl)methyl-1H pyrazolo[3,4 b]- pyridine-5=carboxylic acid ester. 300 g. of 4-hydroxy1-1-(2- furyl)methyl-1H-pyrazolo[3,4-b]-pyridine 5 carboxylic acid ethyl ester (1.05 mol.) are dissolved in 1 liter of dimethylformamide. 210 .g. of potassium carbonate (1.5 mol.) and 233 g. of ethyl iodide are added. The mixture is heated at 60 with continuous stirring for hours. The excess potassium carbonate is filtered 01f. On addition of 500 ml. of water, 4-ethoxy-l-(2-fury)methyl-lH-pyrazolo- [3,4-b]pyridine-S-carboxylic acid ethyl ester preccipitates and is recrystallized from methanol, yield 280 g. (85% m.p. 93-96".

(d) 4-ethoxy-1H-pyrazolo[3,4-b]pyridine carboxylic acid ethyl ester. 31.5 g. of 4-ethoxy-1-(2-furyl)methyl-1H- pyrazolo[3,4-b]-pyridine-5-carboxylic acid ethyl ester (0.1 mol.) and 20 g. of selenium dioxide (0.18 mol.) are suspended in 100 ml. diethyleneglycol dimethylether. The mixture is heated with stirring at 160 and a few drops of water are added. This temperature is maintained for 1.5 hours. After cooling, 100 ml. of water are added and the mixture is neutralized with a dilute solution of aqueous ammonia. Yellow crystals are formed, which yield on recrystallization from methanol 15.8 g. of 4 ethoxy-lH-pyrazolo[3,4 b] pyridine 5 carboxylic acid ethyl ester (67%), m.p. 180.

(e) 4-hydrazino-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester. 2.35 g. of 4-ethoxy-1H-pyrazolo[3,4- b]pyridine-S-carboxylic acid ethyl ester (0.01 mol. are added with stirring to 10 ml. of hydrazine hydrate. Stirring is continued for min. After this time, 50 ml. of water are added and the white precipitate is filtered and recrystallized from n-butyl alcohol, yield 2 g. of 4-hydrazino-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester (f) 4 (2-cyclohexylidenehydrazino)-lH-pyrazolo[3,4- b]pyridine-5-carboxylic acid ethyl ester. 4.4 g. of 4-hydrazino 1H pyrazolo[3,4 b] pyridine-S-carboxylic acid ethyl ester (0.02 mol.) are suspended in ml. of acetic acid and 2 g. of cyclohexanone are added with stirring. The mixture is heated to 80 for 15 minutes. After this time, 4- (2cyclohexylidenehydrazino)-1H-pyrazolo-[3,4- b]pyridine-5-carboxylic acid ethyl ester precipitates on cooling. The product is recrystallized from acetic acid, yield 4.8 g. (80% m.p. 265.

EXAMPLE 40 4-Hydrazino-1H-pyrazolo [3 ,4-b] pyridine-5 -carboxylic acid ethyl ester (a) [[[1 (4 picolyl) 5 pyrazolyl]amino]methy1ene] malonic acid diethyl ester. 174 g. of 1-(4-picolyl)-5-aminopyrazole and 216 g. of ethoxymethylene malonic acid diethyl ester are heated with stirring at 140, until the theoretical amount of alcohol has distilled off. The reaction mixture crystallizes on cooling. Recrystallization from ethyl acetate yields 220 g. of [[[1-(4-picolyl)-5-pyrazolyl] amino]methylene]malonic acid diethyl ester (65% m.p. 97.

(b) 4 hydroxy 1 (4 picolyl) 1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester. 86 g. of [[[1-(4- picolyl)-5-pyrazolyl]amino]rnethylene]malonic acid diethyl ester (0.25 mol.) are heated at 240 for 15 minutes. The dark oil is cooled and 200 m1. of methanol are added. 4 hydroxy 1 (4 picolyl)-lH-pyrazolo[3,4-b]pyridine- S-carboxylic acid ethyl ester crystallizes on standing, yield 33 g. (44% m.p.

(c) 4-hydroxylH-pyrazolo [3,4-b] pyridine-S-carboxylic acid ethyl ester. 3 g. of 4-hydroxy-1-(4-picolyl-1H- pyrazolo[3,4-b]-pyridine-5-carboxylic acid ethyl ester (0.01 mol.) are dissolved in 20 ml. of acetic acid. 2.2 g. of selenium dioxide (0.02 mol.) and 23 drops of water are added. The mixture is refluxed for 30 minutes and then filtered off. 4-hydroxy-1H-pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester precipitates on cooling. Recrystallization from acetic acid yields 1.8 g. (87%), m.p. 275.

(d) 4-ethoxy-1H-pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester. 4.1 g. of 4-hydroxy-1H-pyrazolo[3,4-b] pyridine-S-carboxy acid ethyl ester (0.02 mol.), 5.6 g. of potassium carbonate (0.04 mol.) and 3.5 g. of ethyl iodide (0.022 mol.) are heated in 30 ml. of dimethylformamide with stirring for 10 hours at 60. After this time, the excess potassium carbonate is filtered off and 30 ml. of water are added. 4-Ethoxy-lH-pyrazolo[3,4-b]pyridine-5- carboxylic acid ethyl ester precipitates and is recrystallized from methanol, yield 2 g. (42.5% m.p. 180.

(e) 4-hydrazino-1H-pyrazolo[3,4-g]pyridine-5-carboxylic acid ethyl ester. The product of part (d) is treated with hydrazine hydrate in the presence of zinc chloride as in Example 1(d) to obtain 4-hydrazino-1H-pyrazolo[3,4- b]pyridine-5-carboxylic acid ethyl ester. Upon recrystallization from acetic acid, the product melts above 320.

The following additional products are obtained from the product of part (e) by the procedure of Examples 2 and 4 respectively:

4 (2 isopropylidenehydrazino) 1H pyrazolo[3,4 b]

pyridine-S-carboxylic acid ethyl ester, m.p. 285, recrystallized from n-butyl alcohol.

4 (2-benzylidenehydrazino)-lH-pyrazolo[3,4b]pyridine- S-carboxylic acid ethyl ester, m.p. 270, recrystallized from n-butyl alcohol.

EXAMPLE 41 1-Et l1yl-4- (2-isopropylhydrazino) lH-pyrazolo [3 ,4-b] pyndme-S-carboxylic acid ethyl ester, hydrochloride By substituting an equivalent amount of isopropylhydrazine for the hydrazine in Example 1(d), 1-ethyl-4- (2 isopropylhydrazino) lH-pyrazolo[3,4-b]pyridine-5- carboxylic acid ethyl ester and its hydrochloride are obtained. The hydrochloride melts at 162164.

EXAMPLE 42 1 Ethyl 4 (2-isopropylidenehydrazino)-3-methyl-1H- pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester hydrochloride By substituting 2.2 moles of 1-ethyl-3-methyl-5-aminopyrazole for the 1-ethyl-5-aminopyrazole in Example 1(a) and following the procedure of that Example and Example 2, 1 ethyl 4 (2-isopropylidenehydrazino -3-methyl-1H- pyrazolo[3,4-b]pyridine-S-carboxylic acid ethyl ester hydrochloride hernihydrate is obtained; it melts with decomposition at 197199, it resolidifies at 209 and remelts at 204-205".

- 1 EXAMPLE 43 1 Ethyl 4 (2 isopropylidenehydrazino)-6-methyl-1H- pyrazolo-[3,4-b]pyridine-S-carboxylic acid ethyl ester,

hydrochloride (a) 1 ethyl 6-n1ethyl-4-hydroxy-lH-pyrazolo[3,4-b] pyridine-'5 carboxylic acid ethyl ester. 51.1 g. of l-ethyl-S- aminopyrazole (0.46 mol.) and 101 g. of acetomalonic acid ethyl ester (0.5 mol.) are added to 224 g. of polyphosphorous acid. The mixture is heated with stirring at 120 for three hours. After this period, the mixture is cooled, diluted with 1000 ml. of water and subsequently extracted twice with 300 ml. portions of chloroform. The chloroform layers are collected, dried over sodium sulfate and the solvent is distilled oif. Recrystallization of the residue (67 g.) with petroleum ether yields 1-ethyl-6- methyl 4 hydroxy 1H pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester, m.p. 118120.

(b) 4 chloro l ethyl 6-methyl-1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester. A mixture of 49.1 g. of 1 ethyl 6 methyl 4 hydroxy 1H-pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester (0.197 mol.) and 250 ml. of phosphorous oxychloride is refluxed for 4 hours. The excess phosphorous oxychloride is removed by vacuum distillation and the residue is treated with water. The 4-chloro compound (42g) is filtered under suction and recrystallized from n-hexane, m.p. 545'6.

(c) l-ethyl 4 hydrazino 6 methyl 1H pyrazolo [3,4-b]pyridine-S-carboxylic acid ether ester. To a solution of 10.7 g. of 4-chloro-1-ethyl-6-methyl-1H-pyrazolo [3,4-b]pyridine--carboxylic acid ethyl ester (0.04 mol.) in 160 ml. of benzene and 80 ml. of pyridine are added 4 g. of hydrazine hydrate (100%) (0.08 mol.). The mixture is stirred at room temperature for 7 days. After this period the precipitated hydrazine hydrochloride (2.5 g.) is filtered under suction and the filtrate is evaporated in vacuo at 30 (bath temperature) to dryness. The residue, 1-ethyl-4-hydrazino-6-methyl-1H pyrazolo[3,4-b] pyridine 5 carboxylic acid ethyl ester is recrystallized from ethyl acetate followed by cooling in the refrigerator. On account of ring closure tendency of this compound, the recrystallization temperature is kept below 40, m.p. 126-128", yield 8.1 g. (77%).

(d) 1-ethyl-4-(2-isopropylidene hydrazino)-6-methyllH-pyrazolo [3,4-b]pyridine 5 carboxylic acid ethyl ester. A solution of 5.3 g. of l-ethyl 4 hydrazino-6- methyl 1H pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester (0.02 mol.) in 100 ml. of acetone is kept at room temperature for 6 days. Upon addition of 5 ml. of an alcoholic solution of hydrogen chloride (30 g./ 100 ml.) at room temperature, the hydrochloride of l-ethyl- 4 (2 isopropylidenehydrazino) 6 methyl 1H- pyrazolo[3,4 b] pyridine 5 carboxylic acid ethyl ester precipitates. In order to increase the yield, 100 ml. of anhydrous ether is added to the mixture. Then the hydrochloride is filtered off under suction, washed with anhydrous ether and dried, yield 6 g. (94.5%), m.p. 188-189. Recrystallization from dioxane provides the compound melting at 189-190 By substituting benzoylmalonic acid ethyl ester and phenylacetomalonic acid ester, respectively, for the acetomalonic acid ethyl ester in part (a) above 1-ethyl-4-(2-isopropylidenehydrazino)-6-phenyl 1H pyrazolo[3,4-b] pyridine-5-carboxylic acid ethyl ester hydrochloride and 1-ethyl-4-(2 isopropylidenehydrazino) 6 benzyl-1H- pyrazolo[3,4-b] pyridine 5 carboxylic acid ester hydrochloride are obtained.

EXAMPLE 44 4-[2-(2,2,2 Trichloro 1 hydroxyethyl)hydrazino]-lethyl 1H pyrazolo[3,4-b]pyridine-5-carboxylic acid ethyl ester 2.5 g. of 1-ethyl-4-hydrazino 1H pyrazolo[3,4-b]- pyridine 5 carboxylic acid ethyl ester (0.01 mol.) and 1.8 g. of chloral hydrate (0.011 mol.) are dissolved in 30 ml. of dimethylformamide and the whole is heated at 5560 (bath temperature) for 6 hours. Subsequently the dimethylformamide solution is evaporated to dryness in vacuo. The residual oily product, 4-[2-(2,2,2-trichloro-lhydroxyethyl)hydrazino]-1-ethyl 1H pyrazolo[3,4-b] pyridine-S-carboxylic acid ethyl ester crystallizes quickly, yield 3.8 g., upon recrystallization from ethyl acetate the product melts at 210-212 (dec.).

EXAMPLE 45 4-(2,2 Dimethylhydrazino) 1 ethyl 1H pyrazolo [3,4 b]pyridine 5 carboxylic acid ethyl ester, hydrochloride (a) 4 chloro 1 ethyl 1H pyrazolo[3,4-b1pyridine- S-carboxylic acid ethyl ester. A mixture of 12 g. of [[1- ethyl 5 pyrazolyl)amino]methylene]malonic acid diethyl ester (0.043 mol.) and 70 ml. of phosphorous oxychloride is refluxed for 10 hours. The excess phosphorous oxychloride is removed in vacuo and the oily residue is treated with 50 ml. of water which causes the oil to become crystalline. The solid material is filtered off under suction and dried in a desiccator; yield 8.5 g.'=79% of theory. The 4-chloro-1-ethyl-lH-pyrazolo[3,4-b1pyridine- 5-carboxylic acid ethyl ester is recrystallized from nhexane, m.p. 62.

(b) 4-(2,2-dimethylhydrazino) 1 ethyl-lH-pyrazolo [3,4-b]pyridine 5 carboxylic acid ethyl ester and hydrochloride. To a solution of 25.3 g. of 4-chloro-1-ethyl- IH-pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester (0.1 mol.) in ml. of anhydrous benzene are added 13.2 g. of N,N-dimethylhydrazine (0.22 mol.). This mixture is stirred at room temperature for 7 days. After this time, the separated product is filtered under suction and the filtrate is evaporated to dryness in vacuo. The residual compound is treated with 100 ml. of water and the whole stirred for half an hour so that the product becomes crystalline. 21 g. of 4(2,2-dirnethylhydrazino)- l-ethyl-lH-pyrazolo[3,4-b]pyridine 5 carboxylic acid ethyl ester are filtered under suction, then dissolved in ether. Upon drying the ether solution with sodium sulfate and adding of an ether solution of hydrogen chloride, the hydrochloride of the hydrazino compound is formed, m.p. 166470; upon recrystallization from ethyl acetate, m.p. l74-l76.

By neutralization of the foregoing hydrochloride with aqueous ammonia (10%) there is obtained 4-(2,2-dimethylhydrazino)-1-ethyl 1H pyrazolo[3,4-b]pyridine- 5-carboxylic acid ethyl ester, m.p., 113-115 Recrystallization from cyclohexane provides a compound melting at 114-116.

What is claimed is:

1. A compound of the formula wherein R is hydrogen, lower alkyl or phenyl-lower alkyl, R is hydrogen, lower alkyl or benzyl, R is hydrogen or lower alkyl, R, is hydrogen or lower alkyl, X is hydrogen, phenyl or R R -phenyl-lower alkyl and Y is R R phenyl or R7, R -phenyl-lower alkyl, R-; and R each is hydrogen, halogen, lower alkyl or lower alkoxy, and physiologically acceptable acid addition salts thereof.

2. A compound as in Claim 1 wherein R is hydrogen.

3. A compound as in Claim 1 wherein R is hydrogen or lower alkyl, R; is hydrogen, C to C alkyl or benzyl, R is hydrogen or C to C alkyl, R is hydrogen or C to C alkyl, X is hydrogen, Y is phenyl, chlorophenyl, bromophenyl, benzyl, chlorobenzyl or bromobenzyl, and physiologically acceptable acid addition salts thereof.

4. A compound as in Claim 1 wherein R is hydrogen or lower alkyl, R is hydrogen, ethyl or benzyl, R is hydrogen or methyl, R is hydrogen or methyl, X is hydrogen and Y is phenyl, chlorophenyl, bromophenyl, benzyl, chlorobenzyl or bromobenzyl.

5. A compound as in Claim 1 wherein R and R each is lower alkyl, R R and X each is hydrogen and Y is phenyl.

6. A compound as in Claim 5 wherein each lower alkyl group is ethyl.

7. A compound as in Claim 1 wherein R is lower alkyl, R and Y each is benzyl and R R and X each is hydrogen.

8. A compound as in Claim 7 wherein the lower alkyl group is ethyl.

9. A compound as in Claim 1 wherein R is lower alkyl, R R R and X each is hydrogen and Y is benzyl.

3,736,325 '5/1973 Denzel et al 260295.5 B 3,761,487 9/1973 Hoehn et al 260295.5 B 3,773,777 11/1973 Hoehn et a1 260295.5 B 3,810,904

5/1974 Hoehn et a1 260295.5 B

JOHN D. RANDOLPH, Primary Examiner US. Cl. X.R. 

1. A COMPOUND OF THE FORMULA 